Bit extension



March 19, 1940.

A. R. BONE ET AL BIT EXTENSION Filed Oct. 24, 1938 2 Sheets-Sheet 1 INVE N TOR ARNOLD R. BONE ALI F'RED R ALBRECHT v ATTORNEYS March 19, 1940.R, B NE ET AL 2,193,917

BIT EXTENSION Filed Oct. 24, 1938 2 Sheets-Sheet 8 ,6 i

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' INVENTOR ARNOLD R. BONE I 57 ALFRED PALBRECHT I Wyflw ATTORNEYSPatented Mar. 19, 1940 PATENT Q FFHQE BIT EXTENSION Arnold R. Bone andAlfred P. Albrecht, Wilmington, Ohio, assignors to The Irwin Auger BitCompany, Wilmington, Ohio, a corporation of Ohio Application October 24,19-38, Serial No. 236,780 5 Claims. (Cl. 279-52) The present inventionrelates to certain immovements in extension bits used in connection withbraces, hand drills or screw drivers.

Bi-t extensions. are employed in the art for ind. creasing the effectivelength of a boring bit or screw driver, whereby holes of greater depthmay be bored or screws turned at greater distances. Many devices of thischaracter have been heretofore devised, but they are open to a number ior objections, particularly by way of complicated structure, requiringconsiderable machine work which involves expense. Moreover, adequateprovision has not heretofore been made for the wear of the bit or. screwdriver inserted in the i3 bit extension. It is apparent that, even ifthe slightest play is permitted between the extension and: the bit, thisplay. develops considerable looseness at the joint very quickly due tothe strain at the joint and the long lever distances between the braceand the work surfaces, thus causing eventual detachment of the bit andits extension. Still other prior forms of bit extensions fail to providefor the unevenness or lack of symmetry of the bit at the grippingposition so that the 2'; bit is not firmly seated and held in theextension. Pin and slot arrangements have also heretofore been employedfor holding the adjusting sleeve in. place, and such arrangements otterbecome loosened or detached when the bit is being moved Ito:- in thereverse direction and away from the work surface. The present inventionobviatesall of these difficulties in a practical manner and has for itsprimary object to construct a chuck for extension bits that can be madeof a minimum number of parts, which is compact, strong and willaccommodate bits having different lengths of tapered heads.

Another object is to construct an improved n chuck which automaticallyprovides for the wear or tear in any degree of the head or tang portionof the bit so that a strong gripping action is produced at all times bythe chuck. on the bit.

A- still further object is to provide a' chuck 2.: which maintains itsgrip on the bit when the bit is being turned in either direction, andthe grip is not relaxed until the releasing means is operated.

Other objects and features will be apparent as the specification isperused in connection with so the accompanying drawings, in which-Figure 1 is an elevational. view of the assembly of a bit extensionimproved in accordance with the present invention;

Figure 2 is a perspective, partially broken away,

55- of the main shaft of the bit extension.

Figure 3 is a perspective of the pin Ill.

Figure 4 is a perspective of the clamping ring I.

Figure 5 is a perspective of they clamping jaw member.

Figure 6 is an enlarged end view of the clamping jaws of Figure 5.

Figure '7 is a perspective of the knurled sleeve mounted over theclamping jaws.

Figure 8 is an enlarged sectional view taken along the axis of the bitextension with the jaws out of clamping position, but showing theirre1ative position with. respect to the shoulder of bit;

Figure 9 is a similar view except that the jaws are shown. in theclamping position about the shoulder of the bits;

Figure 10 is. a cross sectional view taken along the line ill-lb inFigure 9, looking in the direction of the arrows; and

Figure 11 is a fragmentary sectional view showing the bit extensionturned approximately forty five degrees from the position illustrated inFigure 9.

Referring to the drawings,v numeral 1" designates. the body portion orshank of the improved bit extension terminating in a rectangular head ortang portion to which is adapted to fit the opening in the chuck of abrace or drill to which it is applied. The body or shank portion isconstituted of a number of sections of different diameters, as shownmore particularly in Figure 2, and terminates at its upper end in arectangularly sl'iapedv opening 2 which is tapered to fit the head of abit 3 or screw driver which necessitates an extension. This opening isof a depth: suificient to leave considerable clearance at the lower endof the bit 3. The upper end of the body portion i is preferably taperedas indicated at 5 in Figure 2 so as to provide a rectangular wall aboutthe opening 2.

Approximately midway between the ends of the body portion i, there is acircular groove 5 which is adapted to receive a snap ring i, the purposeof which will be explained hereinafter. Just above-this groove, anenlargement or collar 8' is provided, the lower edge of which is adaptedto seat itself upon an abutment provided in a casing which surrounds thebody portion and which will be described'presently. Finally, the bodyportion has an opening indicated at 9 (Figure 2), into which isdriven apin is, the purpose of which will also be explained here.- inafter.

Asshown more clearly in Figures 8 to 11 inclusive, the body portion l issurrounded by a sleeve 12 which terminates at its lower end in athreaded portion indicated at 13. The other or upper end carries four ormore jaws M which are shown most clearly in Figure 5. These jaws take onan arcuate form and are separate from one another, except where theyjoin the sleeve and are flared outwardly, as indicated at 15, forreasons which will be explained hereinafter. The metal of these jaws ispreferably treated in such a manner that they have a strong springaction. The jaws terminate at their upper end in an overhanging portionindicated at l6, which is adapted to engage the shoulder portion ll ofthe bit 3 when the jaws are in a compressed condition. The amount ofoverhang is determined by the extent of the shoulder provided on the bit3.

There is also provided an adjustment casing l8 which surrounds thesleeve l2 and has screw threads on its interior surface, which mesh withthe threads on the sleeve. These threads are so biased that, by turningthe casing in a lefthand or clockwise direction, looking down from thetop, the sleeve moves downwardly into the casing.

The sleeve is prevented from rotating with respect to the body portion iby means of the pin It, referred to hereinbefore, which is received by aslot 68 in the threaded portion of the sleeve. The casing i8 is providednear its lower end with an annular ledge indicated at 20, on which abutsthe lower surface of the collar 8 to prevent the body portion i frommoving downwardly with respect to the casing. For preventing movement inthe other longitudinal direction, the casing has, at its lowermostextremity, an undercut groove 2i which provides a seat for the snap ring7. Thus, the collar 8 and the snap ring prevent longitudinal movement ineither direction between the body portion I and the casing i8.

The casing has a roughened or knurled portion on the exterior, asindicated at 22 (Figures 1 and '7), which forms a hand hold by which thecasing is turned. When the knurled portion of the casing is grasped bythe hand and turned to the left, while the body portion l is heldstationary in any convenient manner, the sleeve l2 moves downwardly intothe casing and carries with it the jaws i l. The outside diameter ofthese jaws at their flared portion is such that the jaws contact withthe inside upper edge of the casing that, as the sleeve is moveddownwardly, the flared jaws are compressed or moved inwardly due to therestraining effect exerted by the upper end of the casing. It isapparent that the construction and arrangement of the elements are suchthat the body portion I and the casing l S maintain their relativelongitudinal position with respect to one another and only the sleevemoves longitudinally with respect to these elements when the casing isrotated.

In order to operate the chuck, the jaws M are opened as wide as isnecessary to clear the rectangular head 23 of the bit 3 by turning thecasing l8 as much as is necessary to the right, thus moving the sleevei2 upwardly on the screw threads. The head 23 is then pushed through thejaws into the rectangular opening 2 as far as it will go. The positionof just receiving the bit 3 is shown in Figure 8. After the opening 2has received the head of the bit, the casing I8 is rotated to the left,which, as stated hereinbefore, operates to pull the sleeve downwardlyand to cause the overhanging portion l6 of the jaws M to recede towardthe casing and finally to make a gripping contact with the shoulder llof the bit 3. A gripping action of the most intense character can beobtained by providing the proper fineness of pitch on the screw threads.

As shown more especially in Figures 3 and 5, the jaw portions I6 contactthe shoulders I! only over surfaces of restricted area. Consequently, ifthere is any pitting or other unevenness of this area, the jaws ofrestricted surface can still make a firm contact with the necessaryportions of the shoulder. It will be noted that, in case of extreme wearof the shoulder ll, it is only necessary to give the casing a few extraturns and thereby bringing the jaws IS an additional distance downwardlyto accommodate this wear. It is also evident that this same adjustmenttakes up any wear of the rectangular head 23 or of the rectangularopening 2. The clearance at the bottom of the opening 4 is provided topermit the head of the bit to descend further into the body portion whenoccasion requiresit. In order that the portions I6 of the jaws will seatthemselves as firmly as possible on the shoulder ll, the jaws arearranged preferably along each side of the rectangular opening 2, asshown in Figure 6, so that the corners of the head 23 of the bit extendinto the openings or slots between the jaws. The fact that the jaws arein line with the flat portions of the head 23 and do not encompass thecorners is also indicated in Figure 11, in which a cross section takenthrough the diagonals of the head 23 would not cut any of the jaws asindicated by the lack of cross sectional lines on the jaws.

After the opening 2 has received the head 23 and the jaw portions I6 areplaced in gripping position by rotating the casing l3 to the left, itwill be found that the bit 3 will be held firmly in the chuck and willremain in this position until released by turning the casing to theright. The latter movement causes the sleeve l2 to move upwardly andcarry the body portions I6 away from the shoulder I! due to the springaction of the jaws which are no longer compressed by the upper insideedge of the casing.

It is evident from the foregoing that our improved bit extension is of avery simple character necessitating only three main elements, namely,the body portion I, the combined sleeve and jaw device l2, and thecasing 22. The body portion preferably is made out of forged steel, thesleeves I2 out of casehardened steel in order to impart a springyresilience to the jaws M, and the casing 22 may be made out of coldrolled steel tubing. The amount of machining required on these parts isa minimum. Furthermore, the arrangement is such that any amount ofadjustment may be automatically obtained for taking up wear either onthe shoulder or the head of the bit or in the opening in the bodyportion which receives the head. There is no slot and pin mechanismnecessary in the casing to prevent an accidental release of the jaws,because the jaws cannot open until the casing is rotated. The pin andslot arrangement Ill, I9 is concealed under the casing and is usedsolely for the purpose of preventing the sleeve l2 from being rotatedwhen the casing I8 is being rotated. After the casing has been rotatedto clamping position, the pin and slot actually serve no purpose insofaras the effectiveness of the clamping action is concerned and takes onits function only when the casing 18 is being turned to the releaseposition.

It will be understood that we desire to comprehend within our inventionsuch modifications invention.

Having thus fully described our invention, what we claim as new anddesire to secure by Letters Patent is:

1. In combination, a chuck comprising a body portion having an openingto receive the shank of a bit, a sleeve secured to said portion andadapted to move longitudinally with respect thereto, said sleevecarrying a clamping means for gripping the shoulder of the bit, a casingmounted on the sleeve and adapted to move longitudinally with respectthereto, and means responsive to a recession of the sleeve into thecasing for operating said clamping means and for moving the bit withrespect to said body por-' tion into the opening.

2. In combination, a chuck extension for a bit comprising a bodyportion, a sleeve secured to said portion and adapted to'mo-velongitudinal- 1y with respect thereto, said sleeve carrying a set ofspring jaws for gripping the shoulder .of the bit, a casing surroundingthe sleeve and adapted to compress saidjaws when the sleeve is movedlongitudinally into the casing, and means for causing longitudinalmovement between the casing and sleeve when the casing is rotatedwhereby the jaws are caused to grip the shoulder of the bit and to movethe bit longitudinally with respect to said casing.

3. In combination, a chuck comprising a body portion having an openingto receive the shank of a bit, a sleeve secured to said portion andadapted to move longitudinally with respect thereto, said sleevecarrying a set of spring jaws for gripping the shoulder of the bit, acasing surrounding the sleeve and adapted to compress the jaws when thesleeve is moved longitudinally with closing the jaws to compress andgrip the shoulder of the bit when the sleeve is moved whereby the bit isforced into the opening of the body portion,

4. In combination, a chuck comprising a body portion having an openingto receive. a bit, a sleeve surrounding said portion, means for pre-,

venting rotation between the body portion and sleeve but permittinglongitudinal movement therebetween, said sleeve carrying jaws adapted toengage the shoulder of the'bitupon longitudinal movement of the sleeve,a casing rotatably mounted on the sleeve, means for preventinglongitudinal movement between the body portion and the casing butpermitting rotational movement therebetween, said sleeve and easingbeing provided with screw threads which cause the sleeve to movelongitudinally with respect to the casing and said body when the casingis rotated, and means for compressing the jaws about the shoulderofsaidbit when the sleeve is moved longitudinally whereby the bit isforced into the opening when'the casing is rotated.

5. In combination, a chuck comprising a body,

upon, longitudinal movement of the sleeve, a cas- 1 ing rotatablymounted on the sleeve, said jaws being contained within the casing andextending into divergent directions from one end thereof, the outersurface of said jaws contacting with the inner edge of the casingwhereby, a longitudinal movement of the combined sleeve and jaws causesthe edge of the casing toccmpress the jaws, and means for moving thesleeve longitudinally with respect to said body portion and casingwhereby the jaws clamp about the shoulder of the bit to force the bitinto'the opening of said body portion.

ARNOLD R. BONE. ALFRED P; ALBRECHT.

